Amplifiers, such as audio amplifiers, can produce an undesired output transient signal when operating power or biasing is initially applied to the amplifier, and when power or biasing is removed from the amplifier. A transient signal, commonly referred to as a transient, is typically a spurious sudden pulse of voltage or current of brief duration. The transient may result from many situations, such as a voltage differential on coupling capacitors, circuit imbalances at or within a stage of the amplifier, and abrupt changes in reference voltages. The transients, commonly known as “clicks” or “pops,” may be audibly disturbing to a listener, and can be harmful to output circuitry of the amplifier and to an attached loudspeaker or other electro-acoustical load device.
Techniques have been developed to attempt to prevent or suppress spurious transients, but may fail to address all sources of the transients. Such techniques may attenuate an audible consequence of the transient, but fail to protect all portions of the audio system from damage. These techniques typically include a delay element and a switch used to temporarily limit the gain of the amplifier or isolate the output of the amplifier from a connected load device. Transients can be problematic in any type of amplifier, such as audio amplifiers, radio frequency amplifiers, and industrial and scientific instrumentation amplifiers.
The use of the same reference symbols in different drawings indicates similar or identical items.